GEARED-UP GADGETS

Build five fun gadgets and learn about gears and transmissions. Create a helicopter model with a rotor that spins using a rubber band-powered motor. Assemble a spinner toy that you wind up to launch a fast-spinning top. Make a centripetal force machine that flings its arms outward at high speeds. Build a hand-mixer that demonstrates a gear train. Construct a cool aircraft launcher that flings a model vehicle across the room on a zipline. A 28-page manual guides your model building and experiments with step-by-step illustrated instructions.